Organic second-order nonlinear optical (NLO) materials have received increasing interest due to their promising application in high-speed electro optic (E-O) devices with very broad bandwidth and low driving voltages. One of the most challenging tasks in this area is to effectively translate high molecular nonlinearities (μβ) into large macroscopic E-O activities (r33) in a bulk system. To realize large r33 values, research has been directed toward making chromophores with large dipole moments μ and first hyperpolarizabilities β, increasing loading density of chromophores in a host polymer, and improving poling efficiency.
Recent theoretical analysis has shown that dipole-dipole interactions between chromophores make it impossible to achieve a high degree of noncentrosymmetric order unless undesirable anisotropic intermolecular electrostatic interactions are minimized by steric shape modification of chromophores. A spherical shape has been proposed as means to increase loading density and improve poling efficiency. Dendritic chromophores, NLO dendrimers, and dendronized E-O polymers have recently been developed to isolate the interactions between chromophores and polymers. In comparison with conventional E-O polymers, the screening effect of dendrons allows the chromophores to be spatially isolated, and larger void-containing structures can provide space for efficient reorientation of the chromophores. Furthermore, the globular geometry of dendrimers is well suited for shape modification of chromophores. Although these chromophores have shown encouraging results in improving poling efficiency, pushing the loading density above a certain level (25 to 30 wt %) often results in micro-aggregation and phase separation due to limited miscibility and an incompatibility between chromophores and polymers.
Despite the advances in the development of NLO materials noted above, there exists a need for improved materials and methods. The present invention seeks to fulfill this need and provides further related advantages.